Hygrometer

ABSTRACT

An apparatus for measuring the degree of humidity of a gas which comprises a channel with a sonic neck or throat for the circulation of a stream of gas. An electrical condenser with condenser plates is located in the gas stream in the vicinity of the neck and an electrical measuring device is connected to the condenser to derive therefrom the degree of humidity of the flowing gas bathing the condenser plates.

United States Patent Chatanier et al. May 7, 1974 [54] HYGROMETER 3,424,977 l/l969 Krobath 340/235 2, n 1 Mme-M 32%;; 24:22: 223.12, 2:12:22

Ledru-Rollin, 94-Saint-Maur;.Jacky Robert Leynaert, 11 Avenue du President-Kennedy, 91-Igny; Alain Primary Examiner-Richard C. Queisser Roger Thiriot, 6 Allee Assistant Examiner-Denis E. Corr j M Attorney, Agent, or Firm-Eric H. Waters 92-Chatenay-Malabry, all of France 221 Filed: on. 4, 1971 [5'7] ABSTRACT [21] Appl. No.: 188,684

An apparatus for measuring the degree of humidity of v a gas which comprises a channel with a sonic neck or 5?] 73/333651, throat for the circulation of a stream of gas. An elec d 6 5 5' 336 trical condenser with condenser plates is located in l le 0 4 346 the gas stream in the vicinity of the neck and an electrical measuring device is connected to the condenser to derive therefrom the degree of humidity of the [56] References C'ted flowing gas bathing the condenser plates.

UNITED STATES PATENTS 3,388,596 6/1968 Foley 73/3365 8 Claims, 4 Drawing Figures PATENTEUM 7 I974 OSCILLATOR W'Zf 20 55 SYNC; L.F. DETECTOR AMPLI HYGROMETER The invention relates to a hygrometer.

Various types of hygrometers for measuring the degree of humidity of gases are known, of which some employ the elongation of a hair under the influence of increased humidity, others employ the dew point and yet others the transmission of hyperfrequency oscillations or spectrometry. All these hygrometers are intended to respond to phenomena which vary slowly or very slowly, such as those in question in climatology.

The hygrometer according to the invention, on the other hand, is suitable for providing information relatwater vapor and circulating relative to the said condenser means.

The invention proposes the application of a sonic neck or throat passage for producing a constant flow rate of the gaseous stream which bathes the condenser means.

In one embodiment, the apparatus furthermore comprises means for determining the other factors which, together with the dielectric constant, make it-possible to arrive at the value of the water mass per unitmass of gas. V i

In this respect, the invention contemplates an electrical condenser device which integrates the readings of a condenser means which is sensitive to the dielectric constant of the air and a condenser means which is insensitive thereto, so that it is possible to eliminate the influence of temperature, which simultaneously affects the first and the second means.

The description which follows given by way of an example, relates to the attached drawing wherein:

FIG. 1 is a schematic-view, partly in cross-section, of an apparatus according to the invention;

FIG. 2 is a view, on a larger scale, of a condenser de vice forming part of this apparatus;

FIG. 3 is a view on an even larger scale, and in crosssection, of a component forming part of the same device, the elements of which are spaced apart from one another for better understanding; and

FIG. 4 is an electrical circuit diagram.

The apparatus according to the invention comprises a tubular body of cylindrical external surface 11, and the internal surface 12 of which forms, starting from the outer edge 13, a first convergent nozzle 14 and then a second convergent nozzle 15 which together The odd plates consist of simple metal plates which are parallel to one another and are electrically connected to the upright 24 which carries them.

The even plates are parallel to one another and parallel to the-odd plates. They comprise simple metal plates electrically connected to the upright 25 which supports them.

However, one or more of the even plates consist of two small conducting plates 26 and 27 of the same surface area (FIG. 3) which at one end have perforations 28 and 29 by means of which they are mounted on the upright 25 so as to form an electrically conducting connection therewith. On'their opposing faces 30 and 31 the small plates 26 and 27 are provided with a layer of a dielectric material, 32 and 33 respectively, for example silicon oxide, and said layers are coated with a metal film 34 and 35 respectively. The films 34 and 35 are of lower surface area than the small plates 26 and 27, so that they remain at a distance from the upright 25 and are not connected in an electrically conducting manner therewith. The small plates 26 and 27 thus coated are placed one against the other.

The plate which they form, for example 23 plays the role of a (condenser) plate and cooperates by means of its external faces, 36 and 37 respectively, with the adjacent plates 23 and 23 to form a condenser the dielectric of which consists of the'fluid into which the said plates are immersed, in this instance the gas of the stream 21.

A further condenser is formed by the assembly of the condenser plate which form the two films 34 and 35,

. firstly with the plate 26 and secondly with the plate 27,

with a divergent nozzle 16 define a neck or throat 17,

the divergent nozzle '16 opening into the inner space 18 of a tubular mast 19 to which the body 10 is fixed. A suction is generated through a tube 20 to establish, at the neck 17 and immediately upstream therefrom, a flow of air at the speed of sound.

In this immediate upstream position there are arranged, in the stream 21 thus produced in the body 10, condenser devices generically designed by numeral 22. These devices comprise plates 23, 23 23 etc. (FIG. 2) supported for the odd plates, by a first upright 24 and, for the even plates, by a second upright 25, one of said uprights being grounded, for example upright 25.

the dielectric in this case consisting of the layers 32 and 33, and means being provided for mounting these two condenser elements in parallel.

The number of plates 23 playing this double role is so chosen that on the one hand the first condenser, in which the dielectric is the gas of the stream 21, and secondly the second condenser, in which the dielectric consists of the layers such as 32 and 33, have the same capacity.

Advantageously, the composite plates are distributed over the entire height of the stream 21 so as to take into account the various temperatures which can prevail therein.

The first condenser 41, in which the dielectric is the gas of the stream 21, and the second condenser, 42,

whose dielectric is within the plates, are mounted in the arms 45 and 46 of a measuring bridge 43 (FIG; 4) the common point 44 of which is grounded and the other arms of which consist of the parts 47 and 48 of the winding of a secondary 49 of a transformer 50 the primary 51 of which is connected to the output of an oscillator 52.

The point 53 which is common to the parts 47 and 48 I The electronic devices can advantageously be located within the body as shown schematically at 61, 62 or 63.

The output conductors or cables are arranged within the mast l9.

When the apparatus is intended to be used near a surface of moving water, such as the sea, the front of the cylindrical tubular body 10 is protected by a hemispherical grid 65.

An inlet 64 in the convergent surface 14 makes it possible to obtain the value of the static pressure at any moment.

At least one rapid-response thermocouple 66, fixed to one of the plates of the condenser 22, measures the temperature of the gas. I

The apparatus thus provides all the elements for the desired hygrometric determination.

It covers a range extending to several thousand hertz.

its sensitivity is high.

What we claim is:

1. An apparatus for measuring the degree of humidity of a gas comprising a channel with a sonic neck and means for the circulation of a stream of said gas through said neck at the speed of sound at a constant flow rate and including a covergent portion on one side of said neck and a divergent portion on the other side of said neck, electrical condenser means including condenser plates located in said stream in the vicinity of said neck, said plates extending substantially parallel to the direction of flow of said gas and electrical measuring means connected to said condenser to derive therefrom said degree of humidity.

2. An apparatus according to claim 1, further comprising upstream of the neck and in the vicinity thereof a pipe inlet for measurement of the static pressure of the gas.

3. An apparatus according to claim 1 further comprising a thermocouple on at least one plate of said condenser means for measuring the temperature of the gas of the stream.

4. An apparatus according to claim 1, wherein said condenser means comprises a first condenser, the dielectric of which isthe gas of the stream, and a second reference condenser the dielectric of which is other than said gas.

5. An apparatus for measuring the degree of humidity of a gas comprising a channel with a sonic neck for the circulation of a sonic flow of said gas, a tubular body surrounding said channel and defining therewith a closed space, electrical condenser means including condenser plates located in said stream electronic means located in said space for receiving information provided by said condenser means, electrical measuring means connected to said electronic means to derive therefrom said degree of humidity, and a tubular mast at one end of which is carried said tubular body and at the other end of which is applied suction for circulating said gas.

6. An apparatus for measuring the degree of humidity of a gas comprising a channel with a sonic neck for the plates extending substantially parallel to the direction of flow of said gas and electrical measuring means connected to said condenser to derive therefrom said degree of humidity, said condenser means comprising a first condenser, the dielectric of which is the gas of the stream, and a second reference condenser the dielectric of which is other than said gas, said second condenser being built in at least one condenser plate of the first condenser.

7. Anapparatus according to claim 6 wherein said one plate of the first condenser comprises two metallic layers coated on one side with an insulating material, the two coated surfaces facing each other and being separated by a metallic film which forms one electrode of said second condenser.

8. An apparatus for measuring the degree of humidity of a gas comprising a channel with a sonic neck for the circulation of a stream of said gas at the speed of sound, electrical condenser means including condenser plates located in said stream in the vicinity of said neck, said plates extending substantially parallel to the direction of flow of said gas, electrical measuring means connected to said condenser to derive therefrom said degree of humidity, a tubular body surrounding said channel and defining a closed space therewith, and elecmum.

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECT-ION Q PATENT N6. 3,808,888 DATED May 7, 1974 iN\/ ENTOR( CHATANIER ET AL it is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Add Assignee: -O:Efice National D'Etudes et de Recherches Aerospatiales Signed and Scaled this of August 1978 [SEAL] Attest:

RUTH C. MA DONALD W. BANNER Arresting Ojficer Commissioner of Patents and Trademarks 

1. An apparatus for measuring the degree of humidity of a gas comprising a channel with a sonic neck and means for the circulation of a stream of said gas through said neck at the speed of sound at a constant flow rate and including a covergent portion on one side of said neck and a divergent portion on the other side of said neck, electrical condenser means including condenser plates located in said stream in the vicinity of said neck, said plates extending substantially parallel to the direction of flow of said gas and electrical measuring means connected to said condenser to derive therefrom said degree of humidity.
 2. An apparatus according to claim 1, further comprising upstream of the neck and in the vicinity thereof a pipe inlet for measurement of the static pressure of the gas.
 3. An apparatus according to claim 1 further comprising a thermocouple on at least one plate of said condenser means for measuring the temperature of the gas of the stream.
 4. An apparatus according to claim 1, wherein said condenser means comprises a first condenser, the dielectric of which is the gas of the stream, and a second reference condenser the dielectric of which is other than said gas.
 5. An apparatus for measuring the degree of humidity of a gas comprising a channel with a sonic neck for the circulation of a sonic flow of said gas, a tubular body surrounding said channel and defining therewith a closed space, electrical condenser means including condenser plates located in said stream electronic means located in said space for receiving information provided by said condenser means, electrical measuring means connected to said electronic means to derive therefrom said degree of humidity, and a tubular mast at one end of which is carried said tubular body and at the other end of which is applied suction for circulating said gas.
 6. An apparatus for measuring the degree of humidity of a gas comprising a channel with a sonic neck for the circulation of a stream of said gas at the speed of sound, electrical condenser means including condenser plates located in said stream in the vicinity of said neck, said plates extending substantially parallel to the direction of flow of said gas and electrical measuring means connected to said condenser to derive therefrom said degree of humidity, said condenser means comprising a first condenser, the dielectric of which is the gas of the stream, and a second reference condenser the dielectric of which is other than said gas, said second condenser being built in at least one condenser plate of the first condenser.
 7. An apparatus according to claim 6 wherein said one plate of the first condenser comprises two metallic layers coated on one side with an insulating material, the two coated surfaces facing each other and being separated by a metallic film which forms one electrode of said second condenser.
 8. An apparatus for measuring the degree of humidity of a gas comprising a channel with a sonic neck for the circulation of a stream of said gas at the speed of sound, electrical condenser means including condenser plates located in said stream in the vicinity of said neck, said plates extending substantially parallel to the direction of flow of said gas, electrical measuring means connected to said condenser to derive therefrom said degree of humidity, a tubular body surrounding said channel and defining a closed space therewith, and electronic devices located in said space for the treatment of the information from said condenseR means whereby the electrical path of small differential electrical signals provided by said condenser means is kept at a minimum. 